Amplification of 16S rDNA by nested PCR for measurement of Mycoplasma pneumoniae DNA over time: clinical application.

Mycoplasma pneumoniae (MP) is the most common atypical pathogen that causes respiratory infections in children. Such infections are typically treated by macrolide antibiotics, but the duration of treatment is variable. In this study, we used nested PCR to amplify the 16S rDNA (16S rRNA gene) of MP at different stages of MP pneumonia (MPP) in 100 children who were admitted for lower respiratory tract infections and diagnosed with MPP. Our results indicate that the median duration of MP-DNA positivity was 5 weeks, and 78 % of cases tested positive for 3-6 weeks. Patients with severe disease were positive for MP-DNA for a significantly longer time (median of 6 weeks) than those with mild disease (median of 4 weeks). Thirty-one patients with severe disease who received intravenous immunoglobulin were MP-DNA positive for significantly less time than patients with severe disease who did not receive this treatment. The duration of MP-DNA positivity was prolonged when MP antibody levels were high and treatment was started at a later stage. Therefore, nested PCR can be used for early diagnosis of MP and the duration of MP-DNA reflects the clinical stage of MPP. Early treatment of MPP and the administration of intravenous immunoglobulin during the acute phase of severe MPP shorten the duration of MP-DNA positivity.